Multi-band antenna



y 1956 R. F.-KOLAR ETAL 2,756,420

MULTI-BAND ANTENNA Filed Harsh 23, 1953 2 3 Fi7 j 41 INVENTOR.

ATTORNEY United States Patent MULTI-BAND ANTENNA Robert F. Kolar, 'Collingswood, and John D. Callaghan,

Pennsauken Township, Camden County, N. L, assignors to Radio Corporation of America, a corporation of Delaware Application March '23, 1953, Serial No. 343,973

9 Claims. (Cl. 343-727) This invention relates to antennas and particularly pertains to a combination very-high-frequency and ultrahigh-frequency television receiving antenna.

An object of the invention is to provide a combination very-high-frequency and ultra-high-frequency antenna which needs only a single transmission line from the antenna to the receiving set and which obviates the necessity for isolation networks to combine the frequencies from the several frequency bands.

Another object of this invention is to provide a combination very-high-frequency and ultra-high-frequency antenna of metallic construction which uses a minimum of insulation material, and wherein all parts of the antenna are grounded to the mast for the purpose of lightning protection.

A further object of this invention is to provide an improved combination very-high-frequency and ultra-highfrequency television receiving antenna wherein the matching of the antenna elements to the associated transmission line is achieved by the mechanical configuration of the antenna elements themselves.

Still another object of this invention is to provide a single compact, simply-constructed, mechanically-stable television antenna which may be used for reception of very-high-frequency signals in the range from 54 to 216 megacycles and ultrahigh-frequency signals in the range from 470 to 890 megacycles.

These and other objects are achieved, in accordance with the present invention, by providing a combination very-high-frequency and ultrahigh-frequency antenna which includes two vertically stacked long wire V antennas with a dipole located between the two Vs and electrically connected thereto by conductive connecting elements. From 54 to 88 megacycles, the antenna operates as a dipole with a delta matched feed, utilizing the rear portion of the two stacked long wire V antennas for the delta section. From 174 to 216 megacycles, the rear portion of the V again acts as a delta feed, while the forward extensions of the V antenna tend to effect a current distribution with respect to the dipole to provide colinear action, maintaining a bidirectional directivity characteristic at frequencies considerably greater than the resonant frequency of the base dipole. On the ultrahigh-frequency channels from 470 to 890 megacycles, the antenna acts as two stacked long wire V antennas. The dipole is isolated from the V at these ultra-high frequencies by the reactance of the conductive connecting elements between the dipole and the two V antennas.

A more detailed description follows in conjunction with the accompanying drawing, wherein Figure 1 is a perspective view of the antenna of this invention and Figure 2 is a perspective view of another antenna in accordance with this invention.

Referring to Figure 1, there are shown two spaced long wire V antennas (shown substantially horizontal for the reception of horizontally-polarized waves), one V being composed of the elongated conductors 21, 23, the second V being composed of elongated conductors 25, 27.

The two V antennas are electrically connected together so that their currents add in phase by a short length of transmission line 31, 33. It has been found convenient in practice to make one-half of each V and the associated transmission line out of a single elongated conductor. For example, one arm of the upper V 21, the short transmission line portion 31 and one correspondingly positioned aim of lower V 25 may be a continuous conductor such as aluminum tubing. Antenna terminals 35, 37 are provided in the short transmission line section 31, 33 so that currents in the upper and lower V antennas add in phase with respect to the terminals 35, 37. A twoconductor transmission line 39 which may be a balanced two-wire line is attached to the terminals 35, 37 and extends to the associated radio frequency apparatus, such as a television receiver (not shown).

A substantially horizontally positioned dipole 41 is located between the two Vs 21, 23 and 25, 27 and is connected to both of the Vs at equal distances from the apexes by short conductors 43, 45. The dipole and the Vs are thus triangularly oriented. Stated another way, the dipole is arranged crosswise with respect to each of the sides of the V antennas. The short conductors 43, 45 are made as small as possible so that they will have considerable inductive reactance at the frequency band over which the V antennas are operative.

The dipole 41 is electrically coupled to the transmission line terminals 35, 37 by the rear portions (the portions nearest the antenna terminals) of the two Vs 21, 23 and 25, 27 acting as delta matching section.

A metallic mast 47 may be used to support the entire antenna at the center of the dipole 41. Since the dipole 41 is matched to the transmission line by the delta section using a portion of the two Vs 21, 23, 25, 27, the dipole 41 may be a continuous metallic tubular member for structural strength and the mast 47 is conveniently clamped at the midpoint of the dipole 41.

In an actual embodiment of the invention successfully tried out in practice, an antenna for very-high-frequency and ultra-high-frequency television reception over a band from 54 to 216 megacycles and from 470 to 890 megacycles had the following dimensions: The metallic rods 21, 23, 25, 27 forming the Vs were made each 56 inches long from the projected apex of the V. These rods may be made longer if they can be supported conveniently, and provided that the intercepted wave front is uniform enough that out of phase signals do not create difliculties. The angle of the V between the elongated conductors 21, 23 and 25, 27 was found to be optimum at 48 for 56 inch rods. This angle may be decreased to about 40 or increased to about 60. These limits are determined by a loss of power gain at the lower end of the ultrahigh-frequency band and by pattern break-up at the upper end of the ultrahigh-frequency band. The length of the short conductors .3, 45 preferably should lie between 9 inches and 13 inches. A closer vertical spacing than 9 inches substantially reduces the gain over the band from 470 to 890 megacycles and a spacing wider than 13 inches between the Vs (about one wave-length at 890 megacycles) results in a very sharp vertical polar pattern at the upper end of the ultra-high-frequency band. The slightly broader pattern obtained by the spacing of 9 to 13 inches is more easily oriented on the distant station.

The short conductors 43, 45 were made 12 inches long out of inch outside diameter aluminium tubing. If the diameter of these conductors 43, 45 is made much greater than /8 inch for the dimensions and frequencies given, there will not be sufficient reactance to prevent A inch in diameter, they will not have sufficient mechanical strength to support the 'V antennas, and other supporting members will have to be added. The inductance of the vertical conductors ,43, 4,5 in this configuration is Withifithe liinits 0.03 ,rnicrohenry and 0.6 microhenry.

The dipole 41 should be between 7 feet 6 inches and 8 feet 6 inches long for very-high-frequency television reception. The diameter of this dipole ,is not critical, but is should be large enough to provide ample mechanical strength for mounting and supporting the antenna structure. This dipole 41 was spaced from the projected apex of the two Vs by a distance of 31% inches. The spacing of the dipole is determined mainly by performance of the antenna on the very-high-frequency channels from 54 to 216 inegacycles. If the spacing is made shorter than 26% inches, the horizontal polar pattern on the higher channels of the lowest band (e. g. channel 6, 82 to 88 me acycles in this embodiment) shows break-up. if the spacing of the dipole 41 is greater than 38 inches from the projected apex of the two Vs, the pattern of the higher very-high-frequency channels (e. g. above 200 megacycles) will exhibit break-up.

The V antennas 21, 23 and 25, 27 and the short transmission line section 31, 3:3 were made of inch outside diameter aluminum tubing and the spacing between the transmission line portion 31, 33 was made 2 inches center to center. This spacing with the conductor used correctly matches a transmission line having a characteristic imp edance of 280 ohms. A spacing of this transmission line section 31, 33 from 1 inches to 2 /2 inches will operate satisfactorily with two conductor lines having a characteristic impedance of the order of 15.0 to 450 ohms.

Referring now to Figure 2, there is shown a combination very-high-frequency receiving antenna like that described in Figure 1 except that the antenna of Figure 2 has a reflector added which is mainly helpful in increasing the gain on the lower very-high-frequency television channels (e. g. channels 2 through 6). A reflector 51 is shown paced from the dipole 41. The spacing between the reflector 51 and the dipole 41 is preferably lessthan 0.4 Wavelength (for example, 50 inches or less at channel 6 frequency) so that the antenna will show some gain for the lower very-high-frequency channels (channels 2 through 6). With the dimensions chosen as described above in the specific embodiment of-the antenna, a reflector-dipole spacing of40 inches to 50 inches is satisfactory.

The reflector 51 is supported according to the arrangement of Figure 2 by an arm or crossann 53. The arm 53 may be of either insulating material or of metal, but if metal is used, care must be taken to provide electrical insulation between the terminals 35, 37.

In the structure shown in Figure 2 the mast 47 is connected to the crossarm 53 rather than to the dipole 41. By making the crossarm 53 out of metal and with the reflector element '51 conductively connected to the crossarm 53, all parts of the antenna, including the Vs 21, 23, 25, 27, the dipole 41, the reflector 51 and the arm 53, are-all conductively connected to the mast 47. Lightning protection in such an all-metal antenna may be greatly simplified by merely grounding the mast 47.

More than'one reflector element may be added to the structure of Figure 2 to approach a screen reflector in the same vertical plane occupied by the reflector 51 for the V :antennasZl, '23, 25, 27 as well as for the dipole 41.

What we claim is:

1,. A multiple band antenna comprising a V antenna having an acute angle between the sides thereof and defining agiven plane, a dipole antenna parallel to said given plane but'spa'ced therefrom, short conductive members conductively connecting said dipole antenna on opposite sides of the center of said dipole to the conductors of said V a'ntenna at equal distances from the apex of said V antenna, the closely-spaced ends of said V antenna formingelectr'ical terminals for said V and said dipole.

2. :A mu'ltiple band antenna comprising two V antennas sive V antennas in two parallel spaced planes, a dipole.

in parallel spaced relation, transmission line means conmeeting said V antennas in in-phase relation, a dipole located physically between said V antennas and conductively connected to both arms of both of said V antennas by short metallic members, and terminals at the electrical center of said transmission line means adapted to couple said V antennas to other transmission line means.

3. A multiple band antenna comprising two V antennas in two planes-spaced apart by a distance of substantially one wavelength at the highest frequency to be received, each of said V antennas :having an acute angle between the sides thereof between 40 and 60", a dipole antenna physically located between said V antennas, short conductive members conductively connecting said dipole antenna on opposite sides of the center of said dipole to conductors of both said V antennas at equal distances from their apexes, and means connecting said V antennas together in in-phase relationship, said means having terminals thereon adapted to'have a transmission line connected thereto.

4. A multiple band antenna comprising two V antennas in two parallel planes spaced apart by a distance of substantially one wavelength at the highest frequency to be received, each of said V antennas having an acute angle between the sides thereof between 40 and 60, a dipole antenna physically located between said V antennas, short in two parallel planes spaced apart by a distance of sub-' stantially one wavelength at the highest frequency to be received, each of .said V antennas having an acute angle between the sides thereof between 40 and 60, a dipole antenna physically located betwee'nsaid V antennas, short conductive members conductively connecting said dipole antenna to conductors of both said V antennas at equal distances from their apexes, and a'parallel two-wire transmission line section connecting said V antennas together and having terminals at the electrical centers thereof adapted to have a further transmission line conencted thereto.

6. A multiple band antenna comprising two V antennas in parallel spaced relation, each of said V antennas having an acute angle between the sides thereof between 40 and 60, a dipole antenna physically located between said V antennas, short conductivemembers conductive'ly connecting saiddipole antenna to conductors of both of said V antennas 'at equal distances from their apexes, a re fiector element physically located on the other side of the apexes of said V antennas from said dipole and parallel to said dipole, and a'tra'nsmission line section connecting said V antennas together, said transmission line section having terminals at the electrical center thereof adapted to have a-further transmission line connected thereto.

7. A multiple band antenna comprising two coextenin a third parallel plane intermediate said two planes, said dipole'and said V antennas being triangula'rly oriented, conductive members connecting points on 'said dipole to adjacent points on said V antennas, and means to connect a transmission line to the apexes of said V antennas.

8. A multiple band antenna comprising two V antennas in parallel spaced relation, transmission line means connecting said V antennas in in-phase relation, a dipole located physically "between said V antennas and conductivel-y connected from points intermediate'theends thereof to 'botharms'o'f both of said V antennas by short metallic members, and terminals at the electrical center of V antenna, and means conductively connecting a point on said transmission line means adapted to couple said V the other side of the center of said dipole to an interantennas to other transmission line means. mediate point on the other conductor of said V antenna.

9. A multiple band antenna comprising, a V antenna having two conductors forming an acute angle and defin- 5 References Cited in the file Of this Pawnt ing a given plane, a dipole antenna parallel to said given UNITED STATES PATENTS plane and arranged crosswise with respect to the con- 2 507 225 Scheldorf Ma y 9, 1950 ductors of said V antenna, means conductively connect 2,531,035 Epstein Nov. 21, 1950 ing a point on one side of the center of said dipole to an intermediate point on one of the conductors forming said 10 

